1. Field of the Invention
The present invention relates to a fluid sampling device for medical use capable of taking samples of blood or other fluids from a fluid line such as in an extracorporeal circulation circuit in a medically safe manner.
2. Prior Art
In the past, the following methods have been used to collect blood samples from extracorporeal blood circulation circuits for use in various blood tests.
(1) In dialysis circuits (dialyzers), a hypodermic needle is usually inserted in a rubber medication port in the line. A sample is aspirated with a syringe.
(2) In oxygenator circuits, such rubber medication ports are not used because the internal line pressure is often high. Normally, three-way stopcocks are placed at the sample collection point, and blood samples are collected by switching of the stopcocks. Another reason for not using rubber medication ports is that sample collection is more frequent than on a dialyzer circuit. Because blood gas components, O.sub.2 and CO.sub.2 concentrations, concentrations of K.sup.+, Na.sup.+, C1.sup.-, Ca.sup.++ and other ions, protein concentrations, hematocrit, and other values are frequently measured, there is concern over the durability of the rubber cap. But when three-way stopcocks are used, there is also frequently concern over the possibility of therapeutic problems arising as a result of incorrect operation. Another disadvantage of both methods (1) and (2) is that the syringe must be attached directly to the collection site, which has been inconvenient. For instance, to take a sample from a circuit in which blood is drained from the patient by gravity, one must reach down almost to the level of the floor to carry out the collection procedure.
(3) A method that improves upon the drawbacks of methods (1) and (2) has been devised, whereby slender tubes are led out from the sample collection site to a place where the procedure can be easily carried out. This shall be described later in detail with reference to the figure.
However, one disadvantage common to methods (1), (2), and (3) is the possibility of introducing air into the extracorporeal circulation line as a result of incorrect operation. Operation of the three-way stopcocks in methods (2) and (3) in particular is difficult, making these extremely dangerous in the hands of someone unfamiliar with their use. A similar error may invite the danger of arterial blood, which is under high pressure, spurting from the sampling line.